The present invention relates to matrix-construction padded absorbing article and a method for making said padded absorbing article.
More specifically, the present invention relates to an absorbing construction to be used in disposable sanitary products which are preferably, though not exclusively, used by incontinent women.
As is known, “SAP” is a polymeric material suitable to absorb a comparatively large amount of fluids and to restrain the absorbed fluid under a low pressure.
The above features make said polymeric material suitable for making absorbing structure for incontinence products.
The absorbance efficiency of such a SAP material, in disposable absorbing articles, depends in a high degree on the material shape, position and the manner by which SAP is embedded in the article.
In some cases, in particular as the SAP density is a high one, his efficiency may be negatively affected by the so-called “gel-blocking” phenomenon.
This term is indicative of a situation occurring as the SAP material is in a wet swollen condition, thereby preventing the liquid from arriving at the absorbing article inner parts.
In actual practice the absorbing article absorb the intended fluid with an absorbing rate less than the human body releasing rate, thereby causing excess fluid losses; and this a long time before a full saturation of the SAP material in the article is achieved.
As the SAP material density increases, correspondingly increases the gel-blocking phenomenon.
On the other hand, a high SAP concentration would be desirable to achieve a sufficient article absorbing capability.
Several approaches have been devised to improve the SAP efficiency in absorbing articles, to reduce the above disclosed gel-blocking phenomenon.
Thus, it would be possible to improve the SAP efficiency by causing SAP to assume a spherical configuration in a wet condition.
To hold a typically spherical configuration means to leave inner interstitial free spaces for allowing fluid to enter them.
In addition to the absorbing capability, in particular in a slight incontinence article, the fluid absorption rate is another very important parameter to provide the article with an optimum performance.
In fact, in a typical slight/average incontinence person, the urine flow is characterized by a small amount and high flow rates, since the urine release is related to a temporary control loss by the incontinent person, typically in sneezing, laughing or abrupt effort events.
Thus, in incontinence products, the instantaneous urine acquirement or absorbing rate is much more important than the overall article absorbing capability.
However, an increase of the article absorbing capability, though it would be very desirable, would not be sufficient to assure per se a good operating performance.
For increasing the incontinence article absorbing rate without undesirably reducing the superabsorbing polymer material amount thereof, it is possible to use multiple layer constructions or structures in which the absorbing core parts comprise cellulose fibers with the superabsorbing polymer embedded therein.
To allow the article to operate to transport liquids by a capillarity phenomenon, in which the cellulose fibers would operate as a vehicle for conveying urine to the superabsorbing polymeric material.
However, in actual practice, the above mentioned gel-blocking phenomenon would hinder a proper liquid or liquid diffusion through the article by capillarity.
To overcome such a limitation, it would be also possible to use a so-called distributing or acquirement layer, in addition to the absorbing pad layer proper.
Generally, such an acquirement layer comprises specially processed cellulosic or non woven material fibers, and a comparatively small amount of superabsorbing polymer.
Multiple layer constructions including different superabsorbing polymers in each layer thereof, have also been designed and made.
FIG. 1 shows a prior absorbing pad construction, including a liquid receiving layer 1, not including a superabsorbing polymer, designed for quickly receiving and distributing urine, and an underlying layer 2, constituting the pad proper, with the superabsorbing polymer arranged therein.
As shown, said underlying layer 2 is arranged between two sheet elements, that is a first sheet element 3 permeable to liquids and contacting the user body, and a second sheet element which is a person garment facing impermeable sheet 4.
Such a prior construction comprises moreover a first layer having an urine acquirement but not absorbing function, and consequently undesirably remaining wet and contacting the user skin, which may cause user skin irritating and sensitizing phenomena.
On the contrary, a properly operating absorbing article, should preserve an integral and fully operating condition even if it is in a wet status, which characteristic could be achieved both by binding (by chemical or mechanical methods) the absorbing layer forming fibers, and using fibers having such an average length as to provide, in a interbraided arrangement, a stiff network structure.
However, in actual practice, the above methods excessively stiffen the absorbing pad, thereby undesirably reducing the article softness and comfort properties.
A cotton material has very long fibers and, accordingly, would be ideally suitable to form interbraided and strong absorbing constructions; however a cotton material is not at present used in absorbing articles, since it is much, more expensive than wood cellulose fibers, and cannot be easily processed into absorbing articles, since prior cotton material absorbing articles are conventionally made by overlapping onto one another a plurality of textile fiber web layers deriving from carding processes or formed by blowing or pressing methods in which are used a plurality of cascade arranged carding machines to comb the cotton fibers and form a continuous mattress to be subjected to further cutting and shaping processes.
Moreover, a main limitation of these prior methods is that the absorbing articles made thereby comprise fibers which are oriented in the longitudinal direction of the article and preferably conveying the liquid through a X-Y plane and not in the depth direction of the article.
Another drawback is that of the so-called “hourglass shape” caused by mechanical cutting operations, which undesirably make the pad contour stiffener with objectable aesthetic and a functional characteristics, since said cutting operation cause reddening phenomena at the article user skin contacting points.
Moreover, the constant thickness and basis weight through the overall length of such a prior absorbing article prevent the absorbing material amount and absorbing capability from being properly selected and increased.